Here is how I switched to the mozillateam build (instead of Flatpak):

YMMV, YOUR WARRANTY IS NOW VOID, etc. etc.

If your profile had already been migrated to snap:

mv ~/snap/firefox/common/.mozilla ~/


Remove the snap:

sudo snap remove firefox


Pin the snapping deb to the lowest priority:

printf '%s\n' 'Package: firefox*' 'Pin: release o=Ubuntu' 'Pin-Priority: -1' | sudo tee /etc/apt/preferences.d/99mozillateam


Add the PPA:

sudo apt-add-repository ppa:mozillateam/ppa


Install firefox:

apt policy firefox
sudo apt install firefox